From 3392cd0e98d5c9fdb22846e6ba627085d6b250ef Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Wed, 3 Jun 2026 18:44:19 +0000
Subject: [PATCH] fix(mcp): URL-encode server_id in env-var setup deep link

---
 litellm/proxy/_experimental/mcp_server/utils.py       |  3 ++-
 .../_experimental/mcp_server/test_mcp_env_vars.py     | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/litellm/proxy/_experimental/mcp_server/utils.py b/litellm/proxy/_experimental/mcp_server/utils.py
index dcaa77261cb..97cfa74ea45 100644
--- a/litellm/proxy/_experimental/mcp_server/utils.py
+++ b/litellm/proxy/_experimental/mcp_server/utils.py
@@ -20,6 +20,7 @@ from typing import (
 import hashlib
 import importlib
 import os
+from urllib.parse import quote
 
 # Constants
 LITELLM_MCP_SERVER_NAME = "litellm-mcp-server"
@@ -501,7 +502,7 @@ def interpolate_headers(
 def build_env_var_setup_url(server_id: str) -> str:
     """The frontend URL where a user can fill in their per-user env vars."""
     base = os.environ.get("PROXY_BASE_URL", "").rstrip("/")
-    path = f"/ui/?page=mcp-servers&fill_env_vars={server_id}"
+    path = f"/ui/?page=mcp-servers&fill_env_vars={quote(server_id, safe='')}"
     return f"{base}{path}" if base else path
 
 
diff --git a/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_env_vars.py b/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_env_vars.py
index ffed81d7aa9..d48beeb9069 100644
--- a/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_env_vars.py
+++ b/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_env_vars.py
@@ -106,6 +106,17 @@ def test_build_env_var_setup_url_prepends_proxy_base_url(monkeypatch):
     assert "fill_env_vars=abc-123" in url
 
 
+def test_build_env_var_setup_url_encodes_unsafe_server_id(monkeypatch):
+    from urllib.parse import parse_qs, urlsplit
+
+    monkeypatch.delenv("PROXY_BASE_URL", raising=False)
+    server_id = "a&b=c #d/e"
+    url = _u("build_env_var_setup_url")(server_id)
+    assert "a&b=c #d/e" not in url
+    parsed = parse_qs(urlsplit(url).query)
+    assert parsed["fill_env_vars"] == [server_id]
+
+
 def test_missing_user_env_vars_error_message_is_friendly():
     with pytest.raises(_u("MCPMissingUserEnvVarsError")) as exc_info:
         raise _u("MCPMissingUserEnvVarsError")(